If you saw the red, black and white Sportsman at the Glasair booth at AirVenture this summer, it may not have looked a lot different from the airplanes the company has displayed in the past. But the bright green lettering on the side of the nose and the modified bottom cowl tell a different story. Beneath that cowl is a new engine option — one that more customers around the world and here in the United States are starting to request. If you got close enough to hear the sound of the engine, you might know what I’m talking about — a diesel engine.
For well over a decade, diesel engines have become increasingly popular power plants for piston airplanes. With the high price and lack of availability of 100LL fuels in Europe, it should come as no surprise that a couple of European companies, namely the French SMA with its 230-horsepower SR305 and the German Thielert with its series of Centurion engines, started the recent trend of installing diesel engines into popular airplanes such as Cessnas, Pipers, Diamonds and Socatas, mostly under supplemental type certificates.
Diamond has been the leader in the factory-direct diesel adoption, offering a number of diesel-powered models, including the groundbreaking DA42 light twin.
In the past few years, with the increase in 100LL avgas prices, the diesel concept has also caught on in the United States. Not that U.S. manufacturers haven’t shown interest in the past. Both Continental and Lycoming floated new diesel engine programs more than a decade ago, but no product emerged from either company. Last year, Continental Motors took over the Centurion diesel engine designs from troubled engine maker Thielert.
In addition, there are at least a couple of other homegrown developers, including a company called DeltaHawk that is closing in on certification for a 180-horsepower diesel it hopes to introduce to the market by the end of the year. Wisconsin-based EPS also has a development program in place, for a 350 hp V-8 diesel.
Others are looking to capitalize on the emerging technology. Companies including Premier Aircraft Sales and Redbird Skyport have introduced programs that upgrade legacy Cessna Skyhawks with a series of modifications including an STC installation of the Continental CD-155, formerly the Thielert Centurion 2.0.
After Thielert’s insolvency in 2008, Diamond Aircraft, formerly Thielert’s best customer, started its own engine company, Austro Engines, which today offers a piston diesel power plant similar in concept to Thielert’s.
With a few thousand airplanes now flying behind diesel engines, Cessna and Piper have joined in and announced that they will offer diesel-powered versions straight from their factories.
While diesel engines are emerging as a choice or potential choice among would-be aircraft buyers, the concept is far from new. The first diesel engine that was successfully flown in an airplane was the Packard, which first brought an airplane, a Stinson Detroiter, to the skies in 1928 and was certified in 1930. The Junkers Jumo 205 was also somewhat successful. However, the performance of early diesels didn’t match the gas-piston competition, and with leaded avgas readily available and cheap, diesel engine programs were abandoned.
Despite diesels now making inroads in Part 23 designs, there haven’t been a lot of experimental airplanes with diesel installations. This is possibly due to the fact that one of the major selling points of homebuilt kits is their affordability, and with diesel engines being fairly new, their purchase and maintenance costs are significantly higher. Nonetheless, with the combination of fuel burns being much lower and 100LL prices rising, the option remains tempting.
One homebuilding enthusiast who felt that the benefits of a diesel outweighed the initial cost was Kurt Goodfellow, who worked with Glasair to become the first customer with a diesel-powered Sportsman.
The Sportsman is a remarkable little homebuilt. Glasair introduced the high-wing, single-engine piston-powered plane in 2004. The standard fuselage is made of a combination of fiberglass and carbon fiber, but an all-carbon upgrade is available for an additional cost. The Sportsman is really a 2-plus-2, with two seats up front and two slightly smaller rear-facing seats in the space that also functions as a luggage compartment, which can carry as much as 380 pounds. The bottom parts of the rear seats are removable for those who prefer a larger space for luggage.
Versatility is what best describes the Sportsman. The airplane is certified under an experimental certificate, which allows owners to make modifications and installations more readily than those who own certified airplanes. However, unlike many amateur-built airplanes, the Sportsman can be built quickly. In 2006 Glasair launched Two Weeks to Taxi, a highly organized program that takes the customer to the point of taxiing his or her airplane in, you guessed it, two weeks.
Once it’s complete, you can take the Sportsman just about anywhere you can imagine, from regular runways to rugged fields and gravel bars or lakes and other waterways. Three landing gear configurations are available — tricycle, tailwheel and floats — and the switch from one to another is fairly easy. Going from nose to tailwheel takes only a couple of hours and you can switch to floats in about a day. More than 10 percent of customers choose to buy all three landing gear options, Glasair Vice President Scott Taylor said, and 75 percent choose to take home both the tricycle and tailwheel options. About half of the airplanes are delivered with conventional gear.
If you need to store the Sportsman in a confined space, you can fold the wings on the airplane, making the total width only 10 feet 9 inches — the width of the tail. If you remove the tail, you can make it street legal for transport.
In addition to the standard Superior XP-360 engine, there are several other piston engine and propeller options to add more performance capability. And for the panel, customers can choose Garmin’s G3X, Dynon’s Skyview or Advanced Flight Systems’ AF-5600, including their touch options, without adding any additional cost to the standard Two Weeks to Taxi package. There are also several IFR options available. It seems you can ask anything of the Sportsman and it will deliver.
In 2012, when the Chinese Jilin Hanxing Group purchased Glasair, the company had not introduced a new airplane for about a decade. But under the new ownership Glasair now has the financial backing required to make changes and additions to its product line. One of the programs that is taking shape is the Sportsman Diesel.
With about a quarter of the 420 or so Sportsman airplanes that have left the factory going to international customers, and with avgas becoming increasingly scarce around the world, Glasair saw a potential need for a diesel option. But Taylor said Glasair has seen a surprising number of U.S. customers interested in the diesel option as well.
When Goodfellow expressed an interest in having a diesel engine in his Sportsman, Glasair jumped at the opportunity for a collaborative project. Knowing it to be a proven option, Glasair turned to the Continental CD-155, the same engine that Cessna is in the process of certifying for the 172 Skyhawk. Taylor said Glasair also collaborated with Redbird’s Redhawk team.
The engine in question has a long story for having been introduced only relatively recently. As mentioned earlier, the Continental CD-155 is the former Thielert Centurion 2.0, which is a conversion of a Mercedes-Benz automotive diesel engine. Thielert first certified the 135 horsepower Centurion 1.7 engine in 2002 and replaced it with the 2.0 in 2006. Diamond was its prime customer, and the power plant’s early reception was enthusiastic. Problems soon emerged, however, including reliability and cost issues with the reduction gear box, causing numerous Diamond twins to be grounded. In 2008, Thielert declared insolvency and the company went into receivership. Its founder, Frank Thielert, who had been ousted by the board, was later arrested for fraud.
The good news was that the design of the engine had been greatly improved, and last year, AVIC, parent company of Continental Motors, acquired Thielert.
The newly rebranded CD-155 is certified in 57 countries. Other than the Skyhawk, several STC installations have been approved for the CD-155 engine, including Piper’s PA-28 Cherokee and Diamond’s DA40 and DA42. Continental says there are more than 4,000 Continental diesel engines in operation that have flown more than 4 million flight hours.
The biggest Achilles heel for the engine is that, at this time, it has a recommended time between replacements (TBR) of 1,200 hours. Continental expects the TBR to be increased to 1,800 hours by the first quarter of next year. A U.S. price for a replacement engine has not yet been set by Continental Motors, but Glasair says the engine with the MT propeller, the only one certified for the engine at this time, is $89,750. A Superior XP-360 costs $27,050, but that price does not include a prop. Hartzell is currently working on an aftermarket STC for the CD-155, Taylor said, and once the STC is complete Glasair plans to offer that prop as well.
The Sportsman I flew was configured with a tailwheel (a different airplane than shown), and it is the one owned by Goodfellow. He and Glasair’s Ben Rauk, who was in the right seat during my flight, collaborated on the modification program and spent a couple of weeks in Germany training with the experts on the CD-155 engine.
The biggest engineering dilemma for Glasair during the installation of the CD-155 was getting the temperatures down, Rauk said. Being liquid-cooled, the engine tended to get warmer than desired with the stock cowl.
With the addition of a few new cooling vents, the temperature issue is no longer a problem, Rauk said. But he is still tweaking the final design of the cowl and expects to have it nailed down soon. The airplane can now climb at VY, which is 85 knots in the Sportsman, without overheating when ground temperatures reach as high as 95 degrees, Rauk said. But he hopes to achieve similar results at 105 degrees before calling the cowl design done.
The fadec system that controls the engine has full redundancy with two identical channels — A and B. The engine normally runs on channel A, and if there is a problem with it the system will automatically switch to channel B. However, if for some reason you detect an issue with A you can manually switch to B. Since the engine will not operate without electrical power, redundancy with the power supply is important as well. As a result, there are two alternators, a main battery and a backup battery.
Rauk walked me through the start-up, which is a breeze with the CD-155. The engine has glow plugs instead of spark plugs. All you need to do is watch for an annunciator called a glow light to illuminate and then push the start button. Rauk said that hot starts and starts at high altitudes are just as easy.
As we were rolling down the taxiway I noticed that, even though I was in a taildragger, I had full forward visibility. And, with the fadec, the run-up is very simple. There is no key to turn to the left or right position and no prop lever to mess around with. In order to make sure that the redundant systems are running smoothly, you simply push a button and watch the annunciator lights for the A and B channels turn on and off, indicating the systems are OK. The engine simply checks itself.
The takeoff is equally as simple. There is no mixture control to worry about. The fadec optimizes the amount of jet-A going into the engine. All you need to do is push the load selector (the diesel’s version of a throttle) to the wall and go!
The high rpm of the diesel are definitely noticeable. Having never flown behind a diesel engine before, I can only compare the sound of it to flying an airplane with a Rotax engine. The engine spins at a maximum of 3,890 rpm, but a gear box reduces it to 2,300 rpm for the propeller, and the engine runs smoothly. I felt no vibrations in my feet or back during my flight.
With 155 horsepower versus the 180-horse Superior, the takeoff performance suffers some at sea level. However, the takeoff distance is still well below 1,000 feet, allowing for flights into most backcountry strips, and for airports at higher altitudes, you will see shorter takeoff distances with the turbocharged diesel compared with the Superior since the maximum power is maintained.
During the climb we were burning 8.8 gallons per hour at max power. It wasn’t until right around 9,500 feet that one of the round digital gauges that display the health of the engine indicated a drop in the percentage of power from 100 percent to 99 percent. Monitoring the health of the engine in the Sportsman Diesel is extremely simple as there are green, yellow and red LED lights indicating whether the engine is happy, disturbed or flat-out angry. At no time in the climb did we see temperatures stray from the green on the gauges.
We leveled off at 9,500 feet and saw 140 knots true airspeed quite quickly while maintaining the power control in the full forward position, which gave us 98 percent power and an 8.6 gph fuel burn. Powering back to 85 percent, the propeller dropped to 2,200 rpm, producing a much more pleasant sound. At that power setting we were burning 7.2 gph, and after allowing the airplane to slow down we were cruising at 132 knots true. At 65 percent power we burned only 5.1 gph while seeing 116 knots.
Since the fadec takes care of the optimization of the fuel, you don’t have to lean the mixture, which allows you to spend more time looking outside. You can also apply full power or reduce the power quickly to idle without fear of damaging the engine. Flying this airplane couldn’t be easier. Another great benefit with the fadec is that you can connect a laptop and quickly troubleshoot any problems with the engine.
If you spend most of your time flying at lower altitudes, below 3,000 feet or so, you won’t get much if any performance benefit from the diesel engine, Rauk said. However, above 3,000 feet the CD-155 becomes increasingly more efficient than the 180 horsepower Superior engine. The diesel also appears to use less oil. Rauk said he has added only one quart in 70 hours of flying.
With the engine and the modifications that were required for the new installation, there is an increase in the empty weight for the diesel-powered Sportsman, Rauk said. But he hopes to remove some of that weight before production for the Two Weeks to Taxi program commences soon. The goal is to have 1,000 pounds of useful load with the carbon-fiber fuselage option, which is an upgrade of $15,000.
Along with the slight weight penalty there is also a fairly significant increase in price. The cost for the Sportsman Diesel is $249,000 while the standard Sportsman is $189,250.
However, there are some hidden benefits that are included in the diesel version, such as the constant speed propeller. Glasair is already taking orders for the Sportsman Diesel, and the first Two Weeks to Taxi slot for the new airplane is scheduled on Oct. 27, Taylor said.
Superior XP-360 vs. Continental CD-155
The Continental CD-155 engine installed in the Sportsman Diesel is a completely different animal compared with the Superior XP-360 engine it replaces. Both engines have four cylinders and are duel injected, but that’s pretty much where the similarties end. Here is a direct comparison of the two engines.
View more photos of the Glasair Sportsman Diesel here.
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